I've just booked YUL-YYZ for a short-period in Dec. and welcomed a rather unexpected surprise. After refusing to fly Jetsgo (albeit at $53), I booked on AC flight availability webpage for $79. Yet when it was time to confirm, that portion of the AC website was listing the price as $53. Of course, I booked it immediately - coming to a total of $105 with those annoying fees ($52 worth of fees).

I also booked another flight (YUL-YYZ) for someone else with fares of $76 both ways, yet when time came to confirm, again total cost was $129, indicating that it would have been $53 & $76 each way.

Furthermore, when I went back just 20 mins after booking to see if there had been a change on the flight availability webpage, it was indicating $79 & $104 for those same flights as I had just booked earlier, and when I went to confirm (just for the heck of it), the price scheme added to $183, which would indicate that no such abnormalities had occurred.

Anyone have any idea how such irregularities can occur and how airfares can change so abruptly (ie. $76 to $104) in a matter of minutes, as well as how the flight availability webpage can consistently show $76 airfares, when in fact they are selling for $53 (as on the confirmation page).

The web booking fares are interactive and dynamic. That is to say, fares are not just varied according to current load, but also to current demand. So if you were to query a city pair/time a few times over and over, fares would raise as "demand" is sensed. Then, it takes 15 minutes after each "query" to put the seat back in inventory, thus resetting the fare according to load again.

I ran into that problem a few months ago when booking a group (15) of my buddies on a YYZ-PHX-YYZ trip. As each had to be booked separately, we had to space bookings apart, as the fare kept rising. Going back an hour later, the fare was back where it should be.

I can't really add anything to the irregularities you encountered, but one thing about the Air Canada booking site is that the seat diagram is shown AFTER the user supplies credit card and purchasing details. I would prefer it before so that if a seat which I prefer is not available, I can quickly change the flight, etc. before hand. I realize this is somewhat minor, but other sites allow seat selection prior to actually confirming with payment such as America West.